1. Field of the Invention
The present invention relates to a dynamic bearing device for rotatably supporting a shaft member in a non-contact manner by a dynamic pressure effect of a lubricating oil, generated in a bearing gap. The bearing device is suitable for: a spindle motor for information equipment, for example, a magnetic disk device such as an HDD or an FDD, an optical disk device for a CD-ROM, a CD-R, a CD-RW a DVD-ROM, a DVD-RAM or the like, and a magneto-optical disk device for an MD, an MO or the like; a polygon scanner motor for a laser beam printer (LBP); and a small motor for electric equipment, for example, an axial fan and the like.
2. Description of the Related Art
The above-mentioned various motors are required to operate not only with high rotational accuracy but also at higher speed, lower cost, and lower noise. One of the components determining the required performance is a bearing for supporting a spindle of the motor. As this type of bearing, a dynamic pressure bearing having characteristics excellent in the above-mentioned required performance has been considered for use or has been put into practical use in recent years.
For example, in a dynamic bearing device incorporated into a spindle motor for a disk driving device such as an HDD, the following dynamic pressure bearing is used. The dynamic pressure bearing includes: a radial bearing portion for rotatably supporting a shaft member in a radial direction in a non-contact manner; and a thrust bearing portion for rotatably supporting the shaft member in a thrust direction in a non-contact manner. As the radial bearing portion of the dynamic pressure bearing, a groove for generating a dynamic pressure (a dynamic pressure generating groove) is provided in an inner circumferential face of a bearing sleeve or an outer circumferential face of the shaft member. As the thrust bearing portion, for example, a dynamic pressure bearing including dynamic pressure generating grooves formed in both end faces of a flange portion of the shaft member or surfaces opposed thereto (an end face of the bearing sleeve, an end face of a thrust member fixed to a housing and the like) is used (for example, Japanese Patent Application No. 2002-061641).
The bearing sleeve is normally fixed at a predetermined position on an inner circumference of the housing. In order to prevent a lubricating oil supplied to an internal space of the housing from being externally leaked, a sealing member is sometimes attached onto an inner circumference of an opening at one end of the housing.
The housing used in this type of dynamic bearing device normally includes: a cylindrical side; and a bottom provided at one end of the side. The bottom is not only integrally formed with the side but is also fixed to an inner circumference of one end of the side as a bottom member independent of the side in some cases.
Each of the components of these dynamic bearing devices is cleaned after fabrication so as to remove fine metal powder such as cut powder generated in processing.
In the above-described dynamic bearing devices, press-fitting is conceivable as general means of fixing the sealing member onto the inner circumference of the housing. In press-fitting, however, there is a possibility that abrasion powder such as fine metal power or resin powder (hereinafter, collectively referred to as “abrasion powder”) is generated by a sliding friction between an outer circumference of the sealing member and an inner circumference of the housing along with the press-fitting so as to enter the housing. The abrasion powder entering the housing gets mixed with a lubricating fluid to enter the bearing portion, thereby adversely affecting the performance or the lifetime of the bearing.
Even in the case where the sealing member is fixed by a method other than the press-fitting, there is still a possibility that scoring occurs between the outer circumference of the sealing member and the inner circumference of the housing when the sealing member is pushed into the inner circumference of the housing to similarly generate the abrasion powder.
Although the press-fitting is also general as means of fixing the bottom member onto the inner circumference of one end of the housing, there is a possibility that the above-mentioned abrasion powder is similarly generated by a sliding friction between the outer circumference of the bottom member and the inner circumference of the housing to enter the housing.
An object of the present invention is to prevent the abrasion powder from entering the housing.